It was noted that different ferroelectric domains were degenerate states of the same ferroelectric phase, and were thus energetically equivalent and, in principle there existed no preference for a particular domain pattern. However, the existence of point defects was considered to stabilize certain preferential domain states. In order to study the temperature violation on such stabilized domains, in situ observations were made of an aged K+-doped (Ba,Sr)TiO3 single crystal and it was found that both the domain configuration and polarization state could be memorized after experiencing a thermally activated ferro-para-ferro transition cycle, as manifested by a reappearance of the same domain pattern and double P-E hysteresis loop. In contrast, after the sample was aged in the paraelectric state (>10min), these memory effects disappeared. The above memory effects were considered to originate from the interaction between point defects and the crystal symmetry driven by a symmetry-conforming tendency of point defects. Such a mechanism suggests that the memory effects were relevant to the existence of acceptor dopant and associated mobile oxygen vacancies, and they were not restricted to a particular dopant. Thus similar memory effects were expected to exist in a wide range of ferroelectric materials with acceptor doping.

In situ Observation of Thermally Activated Domain Memory and Polarization Memory in an Aged K+-Doped (Ba, Sr)TiO3 Single Crystal. D.Xue, J.Gao, H.Bao, Y.Zhou, L.Zhang, X.Ren: Journal of Physics - Condensed Matter, 2011, 23[27], 275902